Graded-index fiber

Physics

Cladding (metalworking)

Polarization-maintaining optical fiber

Laser

PHOSFOS

Optics

Femtosecond

Long-period fiber grating

Composite material

Fiber optic sensor

Materials science

Optical fiber

Fiber Bragg grating

Optics Express

We demonstrate a fiber-optic 3D vector displacement sensor based on the monitoring of Bragg reflection from an eccentric grating inscribed in a depressed-cladding fiber using the femtosecond laser side-illumination and phase-mask technique. The compact sensing probe consists of a short section of depressed cladding fiber (DCF) containing eccentrically positioned fiber Bragg gratings. The eccentric grating breaks the cylindrical symmetry of the fiber cross-section and further has bending orientation-dependence. The generated fundamental resonance is strongly sensitive to bending of the fiber, and the direction of the bending plane can be determined from its responses. When integrated with axis strain monitoring, the sensor achieves a 3D vector displacement measurement via simple geometric analysis.

All-fiber 3D vector displacement (bending) sensor based on an eccentric FBG